I have a 1990 GMC K1500, stalling issues.

campjl57
0

Asked by campjl57 Dec 01, 2012 at 07:30 PM about the 1990 GMC Sierra C/K 1500

Question type: Maintenance & Repair

the truck will start up most time fine with a little gas, after about 30 seconds in idle it will do an
irregular idle and then stall out. Also when I put the truck into reverse or drive without my foot on the
gas pedal it will stall out. I can drive the truck as long as my foot is on the pedal giving it a little gas
when I'm at a stop light.
So far I have replace the IAC, PT sensor, ECS module, Ignition module, spark plugs, distributor cap and
wires, fuel pump relay, fuel filter, i have cleaned the carburetor with cleaner spray.Please help!!

18 Answers

John Saffrahn
14,935

Have you tested the fuel pressure? Sounds like the pump is dying.

campjl57
0

So, I changed my fuel filter again and it's running much better but is still stalling, I haven't done a fuel pressure test yet but while I was under changing the fuel filter I saw a pretty major exhaust crack. Do you think this has something to do with the symptoms?

John Saffrahn
14,935

If the exhaust was bent I'd say yea but no not a hole. I'm still betting on the pump.

clubdrink8
10

Bloomington ca.... I have a 90 GMC 1500 5.7 have almost the same problems i dont have the same problem but i dont need to keep my foot on the peddle when you punch it too fast the idle drops and stalls cause its in a high idle i have everything brand new but the fuel pump i was told that it could be the computer i replaced it and its still doing the same thing i took it the mechanic and he had it on computers i was told it was the transmission can i took it to the transmission shop and its okay i was told it could be the wire harness it could be a short so i look at it and still havent found anything yet.... im still stuck on it im getting ready to get rid of the truck!!!

1 out of 1 people think this is helpful.
John Saffrahn
14,935

What is your fuel pumps pressure

1 out of 1 people think this is helpful.
Chris Dutton
20

same here, but my fuel shoots 6 to 8 inches across intake when pump is running. i tried this when throttle body was off. i just replaced fuel pump, fuel filter, new injectors, computer, coil, alt, egr valve, checked every vacuum line and intake for leaks, and it idles fine but soon as rpm gets about 1500 it cuts out really bad and if i floor it it will surge from barely running to high rpm. i cant drive over 35 mph. and would a mufflef that has a bend sideways in it cause this?

1 out of 1 people think this is helpful.
Andrew Olsen
5,705

tps?

John Saffrahn
14,935

Yes a bent exhaust will act exactly like a clogged catalytic converter, light throttle at low rpm is fine but full throttle or higher rpm and the engine can't exhale, it's like trying to hold your breath and suck in more air, eventually you won't have room for more air in your lungs and you can't hold your breath forever. Just unbolt the exhaust and see if it solves your problem.

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John Saffrahn
14,935

An engine under a heavy load consumes about 50% more air than it would in neutral being revved.

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Chris Dutton
20

now when i wiggle the wiring harness going from inner firewall to computer it stops acting bad for a second, but returns back, i have checked every wire in the harness and found no cracks or any broken or frayed wires. all the plugs look good and hold tight, could it be a bad ground somewhere

1 out of 1 people think this is helpful.
John Saffrahn
14,935

You may not see a fault in the wire but it could still be there, I spent quite some time chasing down a bad wire for the ac compressor. Found a hunk of wire that had corroded from the inside, not sure if the wire was nicked or if it got moisture in it when it was made but there was about a quarter inch of the inside that was just a green/white clump of dust. Couldn't find anything wrong with the insulation.

1 out of 1 people think this is helpful.
Tailgunner
15

My 1990 GMC Sierra Single Cab 350 Throttle Body Engine is giving me fits!! At random times the engine just stalls out and it will not start back up for about 45mins to an hour. Afterwards it goes back to running great. The Mechanic stated the Check Engine Light stated bad fuel sensor so that's changed and all electrical components have been changed (Distributor Cap, Rotor, Wires, Spark Plugs etc). Please Help. I get embarrassed broke down in the middle of the street. Thanks.

1 out of 1 people think this is helpful.
John Saffrahn
14,935

You replace the fuel filter? Fuel filters are notorious for getting clogged, stopping the engine, sitting for a while allowing the sediment to settle, and then starting back up like nothing is wrong then running until it clogs again from the debris stirring back up.

Best Answer
John Saffrahn
14,935

Camp you find out what was wrong with yours?

campjl57
0

Fuel pump was spot on. I have another issue with the breaking of my truck. It take for ever to stop. It will not come to a screeching halt and it's a bit dangerous if someone did know how horrible the breaks were. ( I have to stay back a good distance for room) the break pads are good I was wondering if 1990 gmc just have crap breaks to begin with or if there's something I can check or do to improve this problem. -JC

Andrew Olsen
5,705

no, i've had plenty that stop great. Is your ABS activating prematurly? You can feel the pedal pulsating when it does. I had that happen before. Other than that you need to make sure the rear drums are adjusted properly and bleed everything out. Ensure neither of the calipers are stuck

1 out of 1 people think this is helpful.
John Saffrahn
14,935

Yea do what Andrew said also check the rubber lines while someone presses the brake pedal, a swelling/stretching line could reduce the amount of potential pressure resulting in what would seem like a light pedal application could also be a worn master cylinder but I wouldn't go for replacing that until you have definitely ruled everything out.

Greg Sanders
0

on the 5.7 that wont stay running if the temperature sending unit is bad then the truck will not run right or get the right fuel mileage it's located on the housing for the thermostat. there are two of them one is for the gauge and it's on the left head right behind that first plug the other is for the computer

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